1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
In this specification, the semiconductor device generally means any device which can function by utilizing semiconductor characteristics, and an electrooptic device, a semiconductor circuit, and electronic equipment are all included in the category of the semiconductor device.
2. Description of the Related Art
Attention has been focused on a technique for forming a transistor with use of a semiconductor thin film formed over a substrate having an insulating surface (the transistor also referred to as a thin film transistor (TFT)). The transistor has been applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device (display device). A silicon semiconductor material is widely known as a material for a semiconductor thin film applicable to a transistor. As another material, an oxide semiconductor has attracted attention.
For example, a transistor whose active layer includes an amorphous oxide containing indium (In), gallium (Ga), and zinc (Zn) is disclosed (see Patent Document 1).